Recent questions tagged sec-b

An election micro scope uses electrons accelerated by a voltage of 50 kv. Determined the de-Broglie wave length associated with the electrons. If other factor (such as numerical aperture ) are taken to be roughly the same, how does the resolving power of an electron microscope that uses yellow light ?

asked Jun 28, 2016 by meena.p

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Obtain the de-Broglie wave length associated with thermal neutrons at room temperature $27^{\circ}$ Hence explain why a fast neutron beam needs to be thermalised with the environment before it can be used for neutron diffraction experiments.

asked Jun 28, 2016 by meena.p

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Light of intensity $10^{-5} \;wm^{-2} $ falls on a sodium photocell of surface area $2 cm^2$ Assuming that the top 5 layers of sodium absorb the incident energy, estimate the time required for photo electric emission in the wave picture of radiation . The work function of the metal is given to be about 2 ev . What is the implication of your answer ? Effective atomic area $=10^{-20} m^2$

asked Jun 28, 2016 by meena.p

1 answer

ultra violet light of wave length $2271A^{\circ}$ from a 100 w mercury source irradiates a photocell made of molybdenum metal. If the stopping potential is $13.v$ estimate the work function of the metal. How would the photo cell respond to a high intensity $(10^5wm^{-2})$ red light of wave length $6328\;A^{\circ}$ produced by $He- Ne$ laser ?

asked Jun 27, 2016 by meena.p

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The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can perceive . Take the area of the pupil to be about $0.4\;cm^2$ and the average frequency of white light to be found $6 \times 10^4 Hz$

asked Jun 27, 2016 by meena.p

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Estimate the number of photons emitted per second by a Mw transmitter of 10 Kw power emitting radio waves of length 500 m

asked Jun 27, 2016 by meena.p

1 answer

In an acceleration experiment on high energy collision of electrons with position , a certain event is interpreted as annihilation of an electron position pair of total energy $10.2\;Bev$ into two $\gamma$ rays of equal energy. What is the wave length associated with each $\gamma$- ray $(1Bev= 10^9\;ev)$ ?

asked Jun 27, 2016 by meena.p

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An x-ray tube produces a continuous spectrum of radiation with its short wave length end at $0.45 A^{\circ}$ what is the maximum energy of a photon in the radiation ?

asked Jun 27, 2016 by meena.p

1 answer

An electron gun with its anode at a potential $100\;v$ fires out electrons in a spherical bulls containing hydrogen gas at low pressure $(10^{-2}\;mm\;of\;Hg)$ . A magnetic field of $2.83 \times 10^{-4}\;T$ curves the path of the electron in a circular orbit of radius 12.0 cm (The path can be viewed because the gas ions in the path focus the beam by attracting electrons and emitting light by electron capture. this method is known as "fine beam tube " method. Determine e/m from the data .

asked Jun 24, 2016 by meena.p

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A mono energetic electron beam with electron speed of $5.20 \times 10^6 ms^{-1}$ is subjected to a mognetic field of $1.30 \times 10^{-4}\;T$ , normal to the beam velocity .What is the radius of the circle traced by the beam , given $\large\frac{e}{m}$ for electron equals $1.76 \times 10^{11} ckg^{-1}$Is the formula you employ valid for calculating radius of the path of 20 Mev electron beam ? If not in what way is it modified ?

asked Jun 24, 2016 by meena.p

1 answer

A mono energetic electron beam with electron speed of $5.20 \times 10^6 ms^{-1}$ is subjected to a mognetic field of $1.30 \times 10^{-4}\;T$ , normal to the beam velocity .What is the radius of the circle traced by the beam , given $\large\frac{e}{m}$ for electron equals $1.76 \times 10^{11} ckg^{-1}$

asked Jun 24, 2016 by meena.p

1 answer

What is the de-Broglie wavelength of a nitrogen molecule in air at $300\;K$ Assume that the molecule that the molecule is moving with the root- means - square speed of molecules at this temperature ? (Atomic mass of nitrogen = $14.0076\;u$) given : $h= 6.63 \times 10^{-34}\;Js,m_n= 1.675 \times 10^{-27}\;kg; k= 1.8 \times 10^{-23}JK^{-1}$

asked Jun 24, 2016 by meena.p

1 answer

The wave length of light from the spectral emission line of sodium is $589\;nm$ . Find the kinetic energy at which a neutrals would have the same de - Broglie wavelength . given $(h= 6.6 \times 10^{-34}\;Js, mn=1.66 \times 10^{-27}\;kg)$

asked Jun 23, 2016 by meena.p

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Two slits are 1 mm apart and the screen is placed 1 m away. What is the fringe separation when blue green light of wave length 500 nm is used ?

asked Jun 20, 2016 by meena.p

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A beam of light consisting of wave length 650 nm and 520 nm, is used to obtain interference finger in a Young's double slit experiment . Find the distance of the third bright fringe on the screen from the central maximum for wave length 650 nm

asked Jun 20, 2016 by meena.p

1 answer

The $6563 A^{\circ}\; H _{\alpha}$ line emitted by hydrogen in a star is found to be red shifted by $15^{\circ}A$ Estimate the speed with which the star is receding from the earth .

asked Jun 20, 2016 by meena.p

1 answer

A ray of light from a rarer medium strikes a denser medium as shown in the figure . The reflected and refracted rays make an angle of $90^{\circ}$ with each other . The angles of reflection and refraction are r and r' , the critical angle would be

asked Jun 20, 2016 by meena.p

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A star is moving away from an observer with a speed of $500 kms^{-1}$. Calculate the Doppter shift if the wavelength of light emitted by the star is $6000 A^{\circ}$

asked Jun 17, 2016 by meena.p

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If the two slits in young's experiment have width $1:4$ deduce the ratio of intensity at maxima and minima in the interference pattern .

asked Jun 17, 2016 by meena.p

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Two slits $0.125 mm$ apart are illuminated by light of wave length $4500 A^{\circ}$. The screen is 1 m away , from the plane of the slits. Find the separation between the second bright finge on both sides of the central maximum .

asked Jun 17, 2016 by meena.p

1 answer

Consider a light beam incident from air to a glass slab at Brewster's angle as shown. A Polaroid is placed of the emergent ray at a point P and rotated about an axis passing through the center and perpendicular to the plane of the polaroid .

asked Jun 15, 2016 by meena.p

1 answer

The direction of ray of light incident on a concave mirror is shown by PQ, while direction in which the ray would travel after reflection shown in this figure. marked 1,2,3 and 4. Which of the four rays shows the direction of reflected ray ?

asked Jun 15, 2016 by meena.p

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The phenomenon involved in the reflection of radio waves by ionosphere is similar to

asked Jun 15, 2016 by meena.p

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You are given four sources of light each one providing a light of a single colour - red, blue , green and yellow . Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incident at an interface of two media is $90^{\circ}$ which of the following : Statement is correct if the source of yellow light is replaced with that of other lights without changing the angle incident ?

asked Jun 15, 2016 by meena.p

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An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus at the focus . The image

asked Jun 15, 2016 by meena.p

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when a low flying passes overhead , we sometimes notice a slight shaking of the picture on our TV screen . Suggest a possible explanation .

asked Jun 15, 2016 by meena.p

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Two towers on top of two hills are 40 km apart. The line joining then passes 50 m above a hill halfway between the tower . What is the longest wavelength of radio waves , which can be sent between the towers with out appreciable diffraction effects ?

asked Jun 15, 2016 by meena.p

1 answer

In a double slit experiment using light of wavelength $600\; nm$ , the angular width of a fringe formed on a distant screen is $0.1^{\circ}$ What is the spacing between the two slits ?

asked Jun 15, 2016 by meena.p

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Explain : how Newtons corpuscular theory predicts the speed of light in a medium , say water, to be greater than the speed of light in vacuum. Is the prediction confirmed by the experimental determination of speed of light in water ? If not , which alternative picture of light is consistent with experiment ?

asked Jun 14, 2016 by meena.p

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The $6563 A^{\circ} H_2$ line emitted by hydrogen in a star is found to be red shifted by $15^{\circ}$ , Estimate the speed with which the star is reading from earth .

asked Jun 14, 2016 by meena.p

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What is electrostatic shielding ? . How is this properly used in actual practice ? Is the potential in the cavity of a charged conductor zero ?

asked May 30, 2016 by meena.p

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Write briefly the underlying principle used in Davison - germer experiment to verify wave nature of electron experimentally. What is the de- Broglie wavelength of an electron with kinetic energy (K.E) 120 eV?

asked May 30, 2016 by meena.p

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State two properties of electromagnetic waves.How can we show that em waves carry momentum ?

asked May 30, 2016 by meena.p

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Write the functions of a (i) transducer and (ii) repeater in a communication system.

asked May 30, 2016 by meena.p

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The energy levels of a hypothetical atom are shown below. Which of the shown transitions will result in the emission of photon wave length.

asked May 30, 2016 by meena.p

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In the ground state of hydrogen atom, its Bohr radius is given as $5.3 \times 10^{-11}\;m$ . The atom is excited such that the radius becomes $21.2 \times 10^{-11}\;m$ . Find (i) the value of the principal quantum number and (ii) the total energy of the atom in this excited state.

asked May 30, 2016 by meena.p

1 answer

Find the coordinates of the point where the line $ \overrightarrow {r} =(-\hat {i} - 2 \hat {j} - 3 \hat {k} )+ \lambda ( 3\hat i + 4 \hat j +3 \hat k )$ meets the plane which is perpendicular to the vector $ \overrightarrow n= \hat i + \hat j + 3 \hat k$ and at a distance of $\large\frac{4}{\sqrt {11}}$ from origin .

asked May 30, 2016 by meena.p

1 answer

Find the equation of plane passing through the point $A(3,2,1,) B(4,2,-1)$ and $C(6,5,-1)$ and $D(\lambda,5,5)$ are co planar

asked May 30, 2016 by meena.p

1 answer

Given that vectors $ \overrightarrow{a},\overrightarrow{b},\overrightarrow{c}$ from a triangle such that $\overrightarrow{a} = \overrightarrow{b}+ \overrightarrow{c}$. Find p,q,r,s such that area of triangle is $ 5 \sqrt 6$ where $\overrightarrow{a} = p \hat i +q \hat j +r \hat k$ ,$\overrightarrow{b} = s \hat i +3 \hat j +4 \hat k$ and $\overrightarrow{c} = 3 \hat i + \hat j -2 \hat k$

asked May 30, 2016 by meena.p

1 answer

There are two bags A and B . Bag A contains 3 white and 4 red balls whereas bag B contains 4 white and 3 red balls . Three balls are drawn at random ( with out replacement ) from one of the bags and are found to be two white and one red. Find the probability that these were drqwn from bag B.

asked May 30, 2016 by meena.p

1 answer

Solve the equation for $x: \cos ( \tan ^{-1} x ) = \sin \bigg( \cot ^{-1} \large\frac{3}{4}\bigg)$

asked May 27, 2016 by meena.p

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Prove that $ 2\sin ^{-1} \bigg( \large\frac{3}{5} \bigg) - \tan ^{-1} \bigg(\large\frac{17}{31} \bigg) = \large\frac{\pi}{4}$

asked May 27, 2016 by meena.p

1 answer

Ishan wants to donate a rectangular plot of land for a land for a school in his village . When he was asked to give dimensions of the plot, he told that if its length is decreased by 50 m and breadth is increased by 50 m, then its area will remain same. but if length is decreased by 10 m and breadth is decreased by 20 m. then its area will decrease by $5300\;m^2$ . Using matrices , find the dimension of the plot. Also give reasons why he wants to denote the plot for a school.

asked May 27, 2016 by meena.p

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Solve the differential equation : $ 2ye^{x/y} dx+ (y -2x e^{x/y})dy=0$

asked May 27, 2016 by meena.p

1 answer

Solve the differential equation : $(x+1)\large\frac{dy}{dx}$$-y =e^{3x}(x+1)^3$

asked May 27, 2016 by meena.p

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Evaluate : $\int \limits_0^1 \cot ^{-1} (1-x+x^2)dx$

asked May 27, 2016 by meena.p

1 answer

Evaluate: $ \int \limits_0^{\large\frac{\pi}{2}} \large\frac{sin ^2 x}{\sin x + \cos x}$$dx$

asked May 27, 2016 by meena.p

1 answer

Find $\{\int (\log (\log x)+\large\frac{1}{(\log x)^2}\}$$dx$

asked May 27, 2016 by meena.p

1 answer

Find $\int \large\frac{1- \sin x}{\sin x (1+\sin x)}$$dx$

asked May 27, 2016 by meena.p

1 answer

Find the equation of normal to the curve $ay^2 = x^3$ at the point whose x coordinate is $am^2$

asked May 27, 2016 by meena.p

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